It depends. Are you both over state pension age? Do you both receive a state pension now? If your widow does not have her own full state pension the following applies:
Reached your SPA before 6 April 2016
When you die, some of your State Pension entitlements may pass to your widow, widower or surviving civil partner.
Basic State Pension - Your spouse or civil partner may be entitled to some basic state pension based on your National Insurance (NI) contributions but only if they have not already built up a full basic state pension from their own NI contributions record. When you die, your spouse or civil partner can apply for your National Insurance record to be used instead of their own, so this will only help them if your record is more complete than theirs. If you die while they are under state pension age, they will lose this right if they remarry or enter into a new civil partnership before they reach state pension age. Your spouse or civil partner may be entitled to any extra state pension you are entitled to if you put off claiming it when you reached state pension age.